1. Field of the Invention
The invention relates to printing and marking elements and in particular, to a printing and marking element having a shock absorption mechanism.
2. Prior Art
In some printing and marking systems, the objects which are printed upon are fragile and subject to damage by the printing system. While methods for printing on paper are well known, methods for printing on other materials, such as onto goods, are not well known. The reasons for printing directly onto goods vary, but may include the necessity to apply model designations, trademarks, copyright notices, serial numbers, warnings, cleaning or maintenance instructions, country of origin designation or the like. The alternative to printing directly onto goods is to print labels and affix labels to the goods. However, labels are often not permanent despite efforts to make them so.
In the semiconductor industry there is a need to mark housings for transistors and integrated circuits with some of the information mentioned above. Machines have been developed for this purpose which have printing elements which transfer ink obtained from a die directly onto the semiconductor container in one stroke. One such machine has two marking elements, each mounted on opposite ends of a shaft. On an upstroke, the upper element contacts a die and receives ink, after which the downstroke is commenced. Approximately midway through the downstroke the shaft is rotated about a horizontal axis so that the upper element is now coming downward for contacting a housing. The downstroke continues for a predetermined distance, the extent of which is sufficient to permit the marking element to come into contact with the object housing. The marking element in such machines is a pad which serves not only to momentarily retain ink transferred from the die, but also to provide a slight amount of shock absorption.
One problem experienced in the semiconductor industry in using this type of marking machine is that the shock absorption character of the marking pad is insufficient to protect some of the fragile semiconductor housings which are used. For example, ceramic housings are favored in those applications where high temperatures are expected. A ceramic housing is quite brittle compared to a plastic housing, yet is much more expensive than plastic. It has been found that ceramic housings are subject to cracking under the impact of a marking machine. Sometimes these cracks are discovered by optical inspection by a marking machine operator, but in other instances the cracks are microscopic and are only discovered after failure of a device in the hands of a customer, even after final inspection and testing indicate a good part. Replacement of a device in the hands of a customer is very time consuming and expensive both for the customer and the manufacturer.
Accordingly, it is an object of the present invention to devise a printing and marking element for use with fragile goods and other items.